Investigation of a Collisional Radiative Model for Laser-Produced Plasmas

Abstract

Plasmas of a variety of types can be described by the collisional radiative (CR) model developed by Colombant and Tonan. From the CR model, the ion distribution of a plasma at a given electron temperature and density can be found. This information is useful for further simulations, and due to this, the employment of a suitable CR model is important. Specifically, ionization bottlenecks, where there are enhanced populations of certain charge states, can be seen in these ion distributions, which in some applications are important in maintaining large amounts of a specific ion. The present work was done by implementing an accepted CR model, proposed by Colombant and Tonon, in Python and investigating the effects of variations in the ionization energy and outermost electron subshell occupancy term on the positions of ionization bottlenecks. Laser Produced Plasmas created using a Nd:YAG laser with an electron density of ∼ne = 1021 cm−3 were the focus of this work. Plots of the collisional ionization, radiative recombination, and three-body recombination rate coefficients as well as the ion distribution and peak fractional ion population for various elements were examined. From these results, it is evident that using ionization energies from the NIST database and removing the orbital occupancy term in the CR model produced results with ionization bottlenecks in expected locations.

Electron impact cross-sections and rate coefficients of Si+2 ions relevant to collisional radiative modeling of silicon plasma

“…Laser-induced breakdown spectroscopy is one of the well-known diagnostic techniques in which optical emission spectra (OES) coming from the plasma are recorded and analyzed for their characterization [6][7][8][9]. Also, the OES measurements coupled with a suitable collisional radiative (CR) model provide an efficient and noninvasive diagnostic tool to extract detailed information about plasma parameters (n e , T e ), the population distribution of various excited levels of emitting species in the plasma, etc [10][11][12][13][14]. In order to develop a CR model, we need to know the various processes occurring along with their rate coefficients.…”

4f photoabsorption in Pt+ to Pt4+

“…Table 4 shows the weightings applied to the spectra Pt + -Pt 5+ ion stages, for different times after plasma formation, obtained from the CR model. A modified version [27] of the original CR model by Colombant and Tonon was implemented, in which it was shown that the accuracy of estimating the charge state at which ionization bottlenecks occur could be improved by eliminating the occupancy factor, using a different exponent value in the radiative recombination rate coefficient term, and by obtaining experimental values for ionization energies using the NIST database [1], where possible. Fractional ion composition of Pt plasmas with respect to electron temperature between 0 and 15 eV, at a constant electron density of 10 21 cm −3 , acquired using a collisional-radiative model by Colombant and Tonon [26].…”

Special Issue “Interaction of Ionizing Photons with Atomic and Molecular Ions”

“…The final paper [13] by Wong et al investigates the use of the Colombant and Tonon Collisional Radiative (CR) Model for the understanding of laser-produced plasmas. The CR model allows ion distributions for a given temperature and density to be calculated.…”